The pathways of cell activation important to allergy and asthma are being examined by transfecting RBL (rat basophilic leukemia) cells with formyl peptide receptors. This permits the comparison of signal transduction pathways initiated by distinct mechanisms but leading to similar cell response. The primary pathways involve G protein mediated signals initiated by formyl peptide and receptor kinase associated signals initiated by crosslinking of the IgE receptor by antigen. Transfected cells are being characterized by flow cytometry and several aspects of the signalling pathway and motile response have been evaluated. These include actin polymerization, phosphotyrosine kinase activation, and calcium response, all by flow cytometry. Two paper have been published (Hall et al., J. Leuk. Biol. 1997; Lee et al. BBRC, 1997)